It is not unusual to have two or more spool pins side by side.
The extra reason for having one normal (or serrated) driver pin instead of all spools is because the lock goes into false set almost without effort. If the key is tipped to either side at all, the lock binds as the key pins are not able to rise any further, trapping the key. This causes faster lock and key wear, more user frustration, and a reduction in the world coffee supply.

So don't mess with out coffee! Use a normal driver pin instead of all spools!
TrioVing found a way around this by making spools that tapered to full pin diameter in the middle. In the picture below, the two on the right are both TrioVing spool pins, which are also known as barrel pins or trampoline pins. They are far more challenging than you might think.

Gordon
Just when you finally think you have learned it all, that is when you learn that you don't know anything yet.